1. Field of the Invention
The invention relates to a method for assaying sucrose in a sample of biological fluid. This method is useful in a non-invasive diagnostic procedure for detection of gastric damage.
2. Related Background Art
It is currently possible to diagnose gastric damage with great accuracy by a medical procedure known as endoscopy (gastroscopy). However, endoscopy is an invasive and undesirable procedure which is, for several reasons, not practical as a general screening method for gastric damage; patients experience considerable discomfort, the procedure is expensive, time consuming and only available in specialized centers. Typically, patients are chosen for endoscopy when they show symptoms of gastric damage or when gastric damage is apparent by radiology. The major shortcoming of current strategies for diagnosis is that many individuals are asymptomatic for gastric damage. They are, therefore, at risk from potentially fatal complications (e.g. gastrointestinal bleeding) if left untreated.
A method for detection of gastric epithelial damage, particularly ulcers and lesions in the stomach, using non-invasive, non-radioactive and non-x-ray techniques or procedures is disclosed in U.S. Pat. No. 5,620,899. This method employs a disaccharide which can be orally administered to a patient. The disaccharide does not transport across cell membranes, is metabolized within the small intestine to its monosaccharide components, and is not broken down elsewhere in the body. Damage to the gastric epithelium will allow the disaccharide to enter the blood without being metabolized. Hence, the disaccharide will appear in the blood or urine to an extent that can be correlated with the extent of gastric epithelial damage. Typically, the disaccharide is administered to a patient, followed by collection of blood or urine, which is assayed for the disaccharide. The use of sucrose in particular as a diagnostic marker in detection of gastric epithelial damage is described in copending U.S. patent application Ser. No. 08/456,203.
A variety of methods are available for the detection and quantitation of sucrose in biological samples including; gas chromatography, high-performance capillary electrophoresis with indirect absorbance detection or laser interference refractive index detection, high-performance anion exchange liquid chromatography with amperometric detection or refractometric detection and mass spectrum analysis. However, sucrose analysis by these methods is unsuitable for high-throughput screening in the clinical laboratory, either because the methods are expensive, require a high degree of technical skill to perform or require specialized equipment.
Direct immunological assays for sucrose have not been devised. Presumably this is because sucrose is a poor antigen or hapten (i.e., poorly antigenic) or perhaps because antibodies raised against sucrose have poor specificity; possibly cross-reacting with glucose and or fructose. Antibodies with specificity for sucrose have not been reported in the literature. However, antibodies with high affinity and high specificity for polymers of glucose and fructose, the carbohydrates which comprise sucrose, are known. For example, antibodies have been characterized that have high specificity for dextran as well as antibodies with high specificity for levan. Though there are no reports of antibodies directed to glycogen (glycogen is a storage polysaccharide common to all vertebrates and hence unlikely to be antigenic), some well characterized proteins exist which bind specifically to the amylose portion of the glycogen polymer. Most notable of these is the amylose-, or maltose-binding protein of Escherichia coli.
An immunological assay for sucrose, suitable for use in clinical laboratories, would be extremely useful in conjunction with a non-invasive diagnostic procedure for detecting gastric damage.